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Hydrogen embrittlement test piece failures in a cad solution



A discussion started in 2001 & continuing through 2017 -- add your Q to bring it back to the Hot Topics page.

(2001)

Q. Does anybody have any experience of correcting notched tensile test pieces failures used to prove hydrogen embrittlement in a cad solution? The test is 200 hrs @ 75% of the UTS.

Greg Yates
- Manchester, England


(2001)

A. Two things that help:

1. Etch the absolute minimum that you can live with. Abrasive blast if necessary to hold it down. Etch is by far the largest cause of failures in cad plating.

2. Get into the bake oven as soon as possible after plate. To me, that is a maximum of 30 minutes.

James Watts
- Navarre, Florida


(2001)

A. Pre-treat by blasting only. Cadmium solution is to be free of all organics - carbon filter all the time. If your solution has had brightener put in it you will never pass. De-embrittle at 190 °C for 24 hours.


Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England


(2001)

A. I respectfully disagree. Blast and plate, minimum time to bake, bake for 4 hours and ZERO failures, with cyanide cad and acid cad.

James Watts
- Navarre, Florida


(2001)

A. Please can you tell the tensile strength of the steel that you are plating as I am talking of process for cadmium plating of steels in excess of 1450 MPA (210 KSI or 94 ton per inch). I would not treat these for four hours.


Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

(2001)

A. Martin,

I do not remember the exact KSI, but the notch bars were 4340 treated to max hardness with a 400 °F draw temp.

It seems to me that it was a lot higher than 210K, but I do not remember.

To clarify my last response. Time from plate to oven was under 15 minutes. Bake was 375 °F for 4 hours.

Process was abrasive blast, about 1 min in a medium alkaline soak, 10 seconds in a 25% HCl and plate as required.

Notch bars were run with parts and did not receive any special treatment.

Mil Spec certified testing company did the bars.

James Watts
- Navarre, Florida


(2001)

A. Thanks for getting back to me. What I say is you live and learn. I would of thought that four hours was too short a time going by the standards that we work to, but the fact that the test bars pass shows that the method works.


Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England

(2001)

A. A longer bake can be helpful if your parts do not have generous radius or are ground after hardening. The main "secret" is getting them into the oven as soon as possible which limits the depth that the hydrogen can penetrate to.

James Watts
- Navarre, Florida



March 22, 2013

Q. Hi!
I work in the spring industry that frequently requires plating in marine environments. We have several applications where we need a suitable finish (Cadmium) for marine environments with carbon steels but run the risk of hydrogen embrittlement. Are you familiar with materials that can be plated with CAD without running this risk? I am looking into Hard Drawn material over OT and chrome alloys. Any thoughts on circumventing this issue or selecting a proper material?

Tim Roe
- Los Angeles, California, USA


March 25, 2013

A. Hi Tim. First things first. Cadmium is a biocumulative toxin that we all all working to remove from the environment. We never plate with cadmium if we are seeking only one of its properties, like corrosion resistance, because it's possible to simply plate a heavier layer of something else. We use it only if we need the unique combination of properties offered by cadmium including malleability, compatibility with aluminum, freedom from gummy corrosion products, etc. Please carefully consider whether a substitute like tin-zinc or hot dip galvanizing might suffice.

All spring steels are hard and, as far as I know, subject to hydrogen embrittlement. We appended your inquiry to a thread which explains the protocol for hydrogen embrittlement relief. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


March 26, 2013

A. Hi Tim,

To add a bit more to Ted's answer de-embrittlement requirements are usually determined based on either the hardness or the Ultimate Tensile Strength (UTS) of the steel.

In the UK we tend to work on the basis that any steel will require de-embrittlement if its UTS is greater than 1100 MPa (160,000 psi). In the USA it tend to be done on hardness. I have seen varying requirements from 36 HRC to 40 HRC considered the lowest hardness, dependent on the customer.

SAE / AMS2759 [link by ed. to spec at TechStreet] is a good reference source.

Brian Terry
aerospace - Yeovil, Somerset, United Kingdom



June 19, 2017

Q. Is there a way to stop hydrogen embrittlement (ASTM F519 [link by ed. to spec at TechStreet] ) in a pH 9 cleaning solution (surfactant blend) containing nitrite and silicate as inhibitors? Substrate is Cd plated steel.

Rob Crouch
Surfactant Manufacture - Phoenix, Arizona USA


June 2017

A. Hi Rob. I guess I'm not understanding, but why would immersion in a pH 9 surfactant solution be expected to either cause or cure hydrogen embrittlement?

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"

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